This invention relates in general to sound devices and in particular to a new and useful sound chamber closure for an electro-acoustic transducer.
The invention relates to a sound or reverberation chamber closure for an electro-acoustic transducer installed in a housing, in particular an electrodynamic sound generator with a moving oil, which housing is designed to receive a tubular acoustic plug with an acoustic line leading to a stethoscope earpiece, which plug can be introduced into a sound chamber of the housing which closes as the acoustic plug is being pulled out.
A sound chamber closure of the above described kind has been described for example in U.S. Pat. No. 4,028,491. In the subject of this publication the closing occurs by means of a cylindrical jack which upon introduction of the acoustic plug is pushed axially inward into a tubular channel associated with the transducer housing counter to the pressure of a helical spring; and, in the inserted state, clears, via a relatively narrow bore, a sound path to the coupling space before the membrane of the sound generator, so that the sound radiated from the diaphragm can get to the acoustic plug and further via an acoustic line to the stethoscope earpiece. When the acoustic plug has been fully introduced, the last turn of the helical spring touches an electro-conducting, centered disk and an electro-conducting ring disposed concentric therewith and in this manner shortcircuits a resistor present in the circuit of the moving coil of the transducer.
The disadvantages of the known arrangement must be seen in that the sound exit opening is not sufficiently sealed against the penetration of dust and dirt particles into the coupling space and against the radiation of sound which could contribute to molesting the surroundings. Further, the small cross section of the sound path to the acoustic plug constitutes a coupling resistance between diaphragm and acoustic plug, which is not desirable because it causes losses in the sound conduction.